Bobbin case opener for rotating looptaker lockstitch sewing machines



April 21, 1970v K. HEDEGAARD ETAL 3,507,237

BOBBIN CASE OPENER FOR ROTATING LOOPTAKER LOCKSTITCH SEWING MACHINES Filed July 29, 1968 3 Sheets-Sheet l BY /FQQEA r WEA/Z "MEI. 447' A rrvezvgy April 21, 1970 Filed July 29, 1.968

Fig. 3

K. HEDEGAARD ET AL BOBBIN CASE OPENER FOR ROTATING LOOPTAKER LOCKSTITCH SEWING MACHINES 3 Sheets-Sheet 2 INVENTORS re/5 r-z-w #sosaa up FRANZ Owe/05c #5 5527 wawz KAIEL. RAT/4 A fro M 1 y United States Patent US. (:1. 112 1s4 Claims ABSTRACT OF THE DISCLOSURE In a lockstitch sewing machine having a rotating looptaker cooperating with a reciprocatory needle operated by the main drive shaft, said looptaker rotating at a speed equal to a whole number multiple of the speed of said shaft, and a bobbin case frictionally mounted in said looptaker and restrained against rotation thereby by a tongue of said case engaging a stationary abutment, the escape gap for the needle thread loop between said tongue and abutment is opened during the loop-seizing revolutions only of the looptaker by a bobbin case opener intermittently rotating said case in the direction opposite to the looptaker rotation by an opening finger engaging a shoulder of said case along a predetermined operating path. The operating path of the finger is composed ow two coordinate radial and rotational component oscillating movements of said opener derived through separate driving eccentrics, respectively, from the looptaker and main drive shafts. The shape of said path is controlled by the relative adjustment of the eccentrics upon their respective drive shafts.

The present invention relates to rotating looptaker lockstitch sewing machines, more particularly to improved mechanism for the operation of the bobbin case opener forming part of machines of this type and serving to enable a ready passage of the needle thread loop, during the loop-seizing and casting revolutions of the looptaker, through the escape gap between the conventional rotationrestraining tongue of said case and a stationary abutment or notch provided upon the underface of the bed or clothplate of the sewing machine, said tongue being continuously urged, during rotation of the looptaker, against said abutment by the bobbin case being frictionally mounted in the looptaker.

For the foregoing purpose, it is well known to provide a bobbin case opener operated by an opening member embracing an eccentric mounted upon the looptaker shaft, said member having an opening finger adapted to cooperate with a peripheral shoulder upon the bobbin case, to rotate the same in a direction opposite to the direction of rotation of the looptaker, in such a manner as to intermittently open said gap and to allow of a ready escape of the needle thread loop by the upward pull of the thread take-up during each stitch-forming cycle of the sewing machine.

In the effort to ensure a ready escape of the thread through the gap between the rotation-restraining tongue and stationary abutment, various bobbin case opening devices have been proposed in the past, all of which operate by rotating the bobbin case by means of an opening finger extending from the opneing member embracing or otherwise driven by an eccentric upon the looptaker shaft.

More particularly, in the known devices the opening of the needle thread escape gap is effected by the finger of the bobbin case opener operated by the eccentric engaging a peripheral shoulder upon the bobbin case, to rotate said casein a direction opposite to the direction of rotation of the looptaker. As a consequence, the rotationrestraining tongue is impinged against the opposite abutment wall of the rotation-restraining notch, whereby to result in an ever increasing impact or recoil force as the sewing speed is increased. This, in turn, results in an undesirable metallic noise, in a substantial heating of the parts, as well as other defects and drawbacks well understood. Besides, uncontrollable natural oscillations or vibrations of the bobbin case may occur as the speed is increased, liable to greatly interfere with the sewing and stitch-forming operation. Under certain conditions, such oscillations may result in the cutting of the needle thread by a continued hammering efiect thereon by the restraining tongue vibrating between the walls of the restraining notch.

Accordingly, an important object of the present invention is to improve the referred to mechanical bobbin case opener, to substantially eliminate or minimize the afore-mentioned and related difficulties and defects, more particularly, to reduce the impact noise produced by both the rotation-restraining tongue and bobbin case operating finger, especially at the higher sewing speeds, to minimize the recoil force on the tongue upon hitting the wall of said notch, and finally to impede or prevent the setting up of uncontrollable oscillations of said tongue and in turn vibrations of the bobbin case, respectively.

The invention, both as to the foregoing and ancillary objects as well as novel aspects thereof, will be better understood from the following detailed description, taken in conjunction with the accompanying drawings forming part of this specification and in which:

FIG. 1 is an elevation of a rotating looptaker lockstitch sewing machine suitable for structural embodiment therein of the improved bobbin case opener according to the invention;

FIG. 2 is a perspective view illustrating a first embodiment of the improved bobbin case opening device constructed in accordance with the principles of the invention;

FIG. 3 is a sectional view, on an enlarged scale, taken on line IIIIII of FIG. 2;

FIG. 4 is a plan View of a second embodiment of the invention, the looptaker part thereof being shown in section taken on line IV-IV of FIG. 2; v I

FIG. 5 shows, on a greatly enlarged. scale, the composite operating path of the opening finger of the bobbin case opener according to the invention in relation to the shoulder upon the bobbin'case operated by said finger;

FIG. 6 is an elevation, shown partly in section, of a third constructional embodiment of a bobbin case opening device according to the invention; 1

FIG. 7 is a sectional view taken on line VII-VII of FIG. 6; and

FIG. 8 isa view similar to FIG. 7, showing still another practical embodiment for the carrying into effect of the invention.

Like reference characters denote like parts and devices throughout the different views of the drawings. 7

With the foregoing objects in view, the present invention has set itself the task to elfect a continuous force-locking control of a bobbin case opener of the referred to'type by the provision of a predetermined and positive control of the opening finger, in such a manner as to cause an opening of the needle thread escape gap during the loop-' seizing revolutions only of the looptaker within a complete stitching cycle, or main driveshaft revolution of the machine, and to effect a relatively gradual opening yet rapid closing of said gap upon passage therethrough of the needle thread by the pull of the thread take-up, in an efiort'to reduce the impact force by said finger upon the walls of the bobbin case rotation-restraining notch.

The invention, according to one of its aspects, essen tially solves the foregoing problems by the utilization of two eccentric drives for a bobbin case opener of the referred to type, one of said drives operating in synchronism with the looptaker and the other drive operating in synchronism with the main drive shaft of the sewing machine. In other words, the first driving eccentric is driven at a speed equal to a whole number multiple of the speed of the second eccentric conforming with the ratio of the loop-seizing and idle revolutions of the looptaker during a complete stitching cycle, that is, a one to one ratio for most conventional machines. Both said eccentrics are furthermore adjusted relative to one another, in such a manner as to cause the finger of the bobbin case opener to engage the shoulder of the bobbin case during the loop seizing revolutions only of the looptaker, on the one hand, and to cause said finger to initially relatively gradually engage said shoulder, for the opening of the needle thread escape gap, and to subsequently become relatively rapidly disengaged from said shoulder, after escape of the thread through said gap, on the other hand.

The foregoing operation is obtained essentially by a design and relative phase or adjustment of the driving eccentrics of the bobbin case opener, in such a manner as to result in a composite operating path of the control finger including a pair of consecutive bobbin case shoulder-engaging sections of relatively small and relatively large curvature, respectively in the opposite directions and in respect to the edge of said shoulder, to result in the composite operation of said finger as pointed out and as will become further apparent as the description proceeds in reference to the drawings.

Expressed in different words, the component oscillating movement imparted to the bobbin case operating finger by the eccentric operating in synchronism with the looptaker shaft has superimposed upon it the component oscillating movement imparted to said finger by the eccentric operating in synchronism with the main drive shaft of the sewing machine, the relative phase of said movements being adjusted in such a manner that, during the idle or non-loop seizing revolutions of the looptaker, the opening finger is deflected to a limited extent only so as to be unable to contact the shoulder of the bobbin case, on the one hand, and that, during the loop-seizing revolotions of the looptaker, that is, the revolutions during which the looptaker beak seizes and casts the needle thread loop about the bobbin case, the opening finger is deflected or operated along a section of its operating path such as to first effect a gradual contact with said shoulder, for the gradual and smooth opening of the needle thread escape gap with a minimum of noise, and to thereafter effect a relatively quick or instant deflection of the finger in the opposite direction, upon escape of the needle thread through the gap. As a consequence, the needle thread loop is enabled to pass about the bobbin case without substantial obstruction even at the highest sewing speed, while reducing or eliminating impact noise by the opening finger and restraining tongue and preventing other drawbacks and defects of the prior bobbin case opener constructions mentioned hereinabove.

As will be understood, in place of the eccentric drives of the bobbin case opener equivalent devices, such as crank and link mechanisms, may be used for the carrying into effect of the invention. The term eccentric as used for the purpose of this specification and claims is, accordingly, intended to include such equivalents for the conversion of the rotary movements of the looptaker and main drive shafts into the respective bobbin case oscillating movements in accordance with the basic concept of the invention.

According to an improved feature of the invention, the second eccentric controlling the operating path of the opening finger of the bobbin case opener and being driven in synchronism with the main drive shaft, is advantageously adjustably mounted upon its shaft, to enable a control of the shape of said path, to suit existing operating conditions or requirements. In this manner, it is possible, for instance, to control or adjust the operating path of the finger for varying the needle thread escape gap, in an effort to adapt the same to different thread diameters and/ or to adapt the operation to varying sewing speeds.

Referring more particularly to FIG. 1, the numeral 1 indicates the bed or clothplate of a conventional flat-top sewing machine, said bed carrying a housing 2 composed in a known manner of an upright and overhanging arm, the latter terminating in a sewing head and having supported therein the main drive shaft 3 of the machine. Shaft 3 carries, at its outwardly projecting rear end, a hand wheel 4 and is fitted, at its opposite or front end with a crank 5 which serves to operate, by way of a link 6, the needle bar 7 mounted for vertical reciprocation in the head of the machine and carrying a needle 8- at its lower end.

Disposed below the bed 1 is the rotary hook or looptaker drive shaft 9 mounted vertically, in the example shown, and operably connected with the main drive shaft 3 in any suitable manner, such as via a chain belt 10 co operating with a pair of driving and driven chain wheels of like diameter 11 and 12, respectively. Further, secured to the underside of the bed 1 is a mounting support or bracket 13, FIGS. 1 and 2, supporting the looptaker and in the front wall of which is journalled the leading end of the looptaker drive shaft 9. Support 13 includes a horizontal intermediate wall 15 in which is mounted the looptaker assembly collectively denoted by 16 in FIG. 2.

The sewing machine may be equipped with a four-motion or the like feed dog (not shown) for the production of lockstitches in the work being operated on by cooperation of the upper thread-carrying needle 8 with the underthread-carrying looptaker 16, in a manner well known to those skilled in the art.

The looptaker assembly 16 comprises, in the example shown, a hollow looptaker shaft 17, FIG. 3, carrying, at its upper end, the looptaker 18 and having its outwardly threaded lower end secured, through an internally threaded cylindrical bush 19 and by means of a connecting screw or bolt 20, to a bevel gear 21. Bevel gear 21 meshes with further bevel gear 22 being fast on the looptaker drive shaft 9. In the example shown, bevel gear 22 has twice the diameter of the bevel gear 21, whereby the shaft 17 of the looptaker 18 rotates at twice the speed of the drive shaft 9, or main shaft 3, respectively. In other words, the looptaker 18 performs two revolutions during each stitching cycle or complete reciprocation of the needle 8, in accordance with the operation of conventional rotary looptaker sewing machines. As is understood, in machines involving a multiple looptaker rotation exceeding twice the number of needle reciprocations, the bevel gears 21 is designed for a corresponding speed relative to the gear 22.

Mounted between the cylindrical hub of the bevel gear 21 and bracket 15 are a pair of ball bearings 23, and disposed within the cup-shaped looptaker 18 is a bobbin case 24 having a peripheral rib journalled in a corresponding guide groove in the interior surface of the looptaker of conventional construction. Applied to the outer end of the hollow central shaft of the bobbin case 24 is a snap cover or cap 26 secured in place by means of a pivoted locking lever 27. The bobbin case, which in a known manner houses the bobbin containing the underthread, is fitted upon its periphery ith a rotation-restraining tongue. 28 projecting into a rotation-restraining stationary abutment in the form of a notch 30 disposed upon the underface of the stitching plate 29 of the sewing machine secured to the bed 1. As a consequence, the bobbin case 24, being normally urged, by friction with the looptaker, against One of the walls of the notch 30, that is, the Wall spaced from said tongue in the direction of looptaker rotation, is limitative rotatable relative to the looptaker, that is, within the walls or abutments of the notch 28.

The upper end of the looptaker shaft 17 has the form of an eccentric 31 fitted upon its upper face with follower pins 32 which project into corresponding recesses in the looptaker bottom 18. Cooperating with the eccentric 31, by way of a ball bearing 34, is an eccentric ring 35 having an eccentric arm 39 and acting as a bobbin case opener in the manner described and explained in greater detail in the following in reference to FIGS. 2, 3, 4 and 6. For this purpose, the ring or opener 35 is fitted with a peripheral upwardly extending control finger 36 angularly bent at its upper end and adapted to cooperate with a projection or shoulder 37 upon the periphery of the bobbin case 24, to intermittenly rotate the latter in a direction opposite to the rotation of the looptaker 18 and to thereby open the needle thread escape gap between the tongue 28 and its abutment wall of the notch 30. This, in turn, will allow of a ready passage of the needle thread during its upward .pull by the thread take-up of the sewing machine in the course of a stitch-forming operation or cycle. The entire looptaker assembly 16, together with the ball bearings 233, is mounted by press-fit enegagement or otherwise in the wall or bracket of the support 13 and secured against axial displacement by means of a cover or washer 38, FIGS. 3 and 6, applied to the outer ring of the ball bearing 23.

Rotatively connected, by means of a tapped pin 42, to the eccentric arm or extension 39 of the bobbin case opener is the fork-shaped end 40 of a link 41 whose opposite end is in turn rotatively connected, by means of a tapped pin 43, to an intermediate member 44 secured, preferably by clamping, to a push rod 45 being parallel to and slidably mounted in the support 13 in the work feed direction of the machine indicated by the arrow V in the drawing.

Further secured to the rod 45 is an intermediate member 46 to which is linked, by means of a tapped pin 47, the end of an eccentric arm 48 whose opposite ringshaped end embraces an eccentri 49 adjustably mounted, in any suitable manner, upon the looptaker drive shaft 9, whereby to be rotated in synchronium with the main drive shaft 3.

According to an alternative embodiment of the invention as shown by FIG. 4, the linkage mechanism of FIG. 2, connecting the eccentric 49 with the bobbin case opener 35 and comprising the eccentric arm 48, push rod 45 and link 41, is replaced by a link 51 having one end rotatively connected, by means of a pin or bolt 50, to the eccentric arm 39 of the bobbin case opener 35, with the opposite end of the link 51 embracing the eccentric 49. The latter is preferably adjustably mounted upon the end of a vertical shaft 52 being spaced from and parallel to the looptaker shaft 17 and suspended from the bed 1 of the machine. Secured to the shaft 52 is a first bevel gear 53 which meshes with a second bevel gear being of equal size 54 to the gear 53 and fast upon the looptaker drive shaft 9. As a consequence, the shaft 52 and eccentric 49 rotate with the same speed as the main drive shaft 3.

According to a further modification as shown by FIGS. 6 and 7, the driving eccentric 49 of the bobbin case opener according to FIG. 4 is adjustably mounted upon a shaft 56 supported by the bracket 13 and secured against axial displacement by means of a setting ring 55. The axis of rotation of the shaft 56 coincides with the axis of the looptaker shaft 17 and carries at its upper end a bevel gear 57 meshing with an equal-sized bevel gear 58 fast on the looptaker drive shaft 9. The eccentric 49 cooperates with the ring-shaped end of an eccentric arm 59 whose opposite end is rotatively connected, by means of a pin 60, to a crank 61 secured to a vertical shaft 62, the latter being journalled in the support 13 and carrying at its upper end a further crank 63. Both cranks 61 and 63 form an angular lever 64 rotatable about the shaft 62 and secured against axial displacement by means of a setting ring 65. Rotatively connected, by means of a pin 66, to the crank 63 is an end of a link 67 whose opposite end is in turn rotatively connected, by means of a pin 68, to the eccentric arm 39 of the bobbin case opener 35.

Referring to the fourth modification of the invention as shown by FIG. 8, the bobbin case opener 35 according to the previously described embodiments is replaced by a pull rod or bar 69 having one (ring-shaped) end mounted upon the eccentric 31 of the looptaker shaft 17 and having its free end rotatively connected, by means of a pin 70, to the end of a link 71 whose opposite ring-shaped end embraces the driving eccentric 49. The link 71 is extended in the opposite direction from its pivot 70 as shown in 72 and bent at its free end to act as bobbin case opening finger 36 for cooperation with the bobbin case shoulder 37, in the manner as described hereinbefore. Alternatively, a separate opening finger may be connected to the extension arm 72. According to this embodiment, the eccentric 49 is mounted upon a vertical shaft 73 journalled in the support 13 and driven by a bevel gear pair 74 and 75 by and in synchronism with the looptaker drive shaft 9.

The operation of the sewing machine according to the afore-described embodiments is as follows.

Rotation of the main drive shaft 3 by a conventional driving motor (not shown) causes the needle bar 7 to be reciprocated in a vertical direction by the crank 5 and link 6, whereby the needle 8 affixed to the lower end of the bar 7 cooperates with the looptaker 18 driven, by way of belt 10, Wheels 11, 12, looptaker drive shaft 9 and bevel gear pair 22-21, to rotate twice per revolution of shaft 3 or each complete reciprocation of the needle 8, for the formation of lockstitches in the work being operated on. During this operation, the needle thread loop seized by the looptaker beak is cast about the bobbin case 24, more particularly, by the work limb of said loop being led over the undersurface and by the needle limb of said loop passing over the upper face of the bobbin case 24. Inasmuch as the latter, due to the friction between its peripheral supporting rib and the guide groove in the internal surface of the looptaker, is urged in the direction of rotation of the looptaker, whereby to cause its rotationrestraining tongue 28 to engage the abutment wall of the stationary notch 30 spaced from said tongue in the looptaker rotating direction, it is necessary, in order to ensure an unimpeded casting of the needle thread loop about the bobbin case 24, to provide for ready passage of the needle limb of said loop through the escape gap between the tongue 28 and the abutment wall of notch 50, by the briefly intermittently rotating the bobbin case in the direction opposite to the rotating direction of the looptaker. This escape gap opening control results in the shoulder 37 being hit suddenly by impact with the finger 36, causing thereby a suflicient opening of the gap between the tongue 28 and the abutment wall of the notch 30, to allow of a ready and unimpeded escape of the needle limb of the needle thread loop under the effect ofthe upward pull upon the thread by the thread take-up lever of the sewing machine.

As a consequence, the bobbin case opener 35 according to the first, second and third embodiments described in the foregoing, being mounted, via the ball bearing 34, upon the eccentric 31 rotating in synchronism with the looptaker 18, has imparted to it, during the operation of the machine and by virtue of the connection, by means of pin 42, of the arm 39 of member 35 to the link 41 (first embodiment), or to the link 51 by means of pin 50, (second embodiment), or finally to the link 67 by means of pin 68 (third embodiment), respectively, a continuous radial oscillating movement in respect to the looptaker shaft or axis 17, to which component movement is added a rotational oscillating component of the bobbin case opener 35 about the eccentric 31 in synchronism with the rotation of the main drive shaft 3 and by way of the eccentric 49, eccentric arm 48, clamping member 46, slide rod 45, clamping member 44 and link 41 (first embodiment), or by way of link 51 (second embodiment), or by way of the eccentric arm 59, angular lever 64 and link 67 (third embodiment), respectively.

In the fourth embodiment, FIG. 8, there is imparted to the end or finger 36 of the extension 72 of link 71, said finger cooperating with the shoulder 37 on the bobbin case, a first oscillating component movement about the eccentric 49 upon shaft 73 and by way of the pull bar 69 embracing the eccentric 31, on the one hand, and being connected to link 71 by the pin 70, on the other hand. Superimposed upon this first component movement by way of link 71 and pivot is a further oscillating component derived from the eccentric 49 rotating in synchronism with the looptaker drive shaft 9, said further component being directly imposed upon the link 71 by its end embracing the eccentric 49.

Inasmuch as the looptaker 18 seizes and casts the needle thread loop about the bobbin case 24 during each alternate looptaker revolution only, and besides, since the impact speed of the finger 36 upon the shoulder 37 should be a minimum, and furthermore, the release of the shoulder 37 after passage of the needle thread loop should be as quick as possible, the mutual adjustment of the driving eccentrics 31 and 49 of the bobbin case opener 35 is such, in accordance with the basic concept of the present invention, that the finger 36, or a point thereof, respectively, follows a resultant predetermined course or operating path, per each revolution of the main drive shaft 3 or stitch-forming cycle of the machine and by superimposition of both driving movements of the eccentrics 31 and 49, rotating at different speeds, as shown by FIG. 5 on a greatly enlarged scale, said composite operating path comprising the successive sections A (between points and 4), B (between points 4 and 5), C (between points 5 and 6), and D (between points 6 and 12 or 0). During this complete operating cycle of the finger 36, only sections B and C engage or intersect the edge of the shoulder 37, section B having a relatively small curvature towards said shoulder and section C having a substantially greater curvature in the opposite direction or away from the shoulder 37.

More particularly, the finger 36 follows, during the loop-seizing and casting revolutions of the looptaker 18, a path comprising the sections A, B and C shown by full lines in FIG. 5, while the path of the finger 36 during the alternate or idle looptaker revolutions follows the curve or section D indicated by the dotted line in the drawing.

While the finger 36 disposed at the end of link 71, FIG. 8, follows a somewhat different path, the corresponding portion of the path or engagement of the finger 36 with the shoulder 37 substantially follows the course of sections B and C shown in FIG. 5.

From the foregoing it follows that the finger 36 engages the shoulder 37 of the bobbin case 24 during the loop-seizing revolutions of the looptaker 18 only. In other words, the bobbin case 24 is operated by the finger 36 in the direction opposite to the direction of rotation of the looptaker during every second looptaker revolution only, to allow of the escape of the needle thread loop through the gap formed by the rotation-restraining tongue 28 and the abutment wall of the notch 30. After the thread has escaped through the gap as a result of its upward pull by the thread take-up, the shoulder 37 is released from the finger 36, thus allowing the bobbin case to return to its operative position or position of engagement between the tongue 28 and wall of the notch 30 spaced from the tongue in the looptaker rotating direction.

More particularly, the finger 36, as more clearly shown in FIG. 5, engages the shoulder 37 at a point within section B of the operating path, that is, approximately at point 4 of said path. As pointed out, section B has a relatively small curvature towards the shoulder 37 (between points 4 and 5), with the result that the finger initially engages the shoulder at a relatively low speed and wiping engagement therewith, whereby to reduce its impact upon the shoulder to a minimum. As a consequence, the bobbin case 24 is rotated relatively slowly or gradually in the direction opposite to the direction of rotation of the looptaker 18. Since, furthermore, the bobbin case, together with its tongue 28, now engages the opposite wall of the notch 30, or wall spaced from the tongue 28 in the direction opposite to a looptaker rotation, with greatly reduced speed or impact, the recoil force upon the tongue 28 is reduced to a minimum, substantially preventing thereby the setting-up of uncontrollable natural oscillations of the case 24, as Well as damage to or breakage of the thread by the impact of the tongue 28 upon the walls of notch 30. At the same time, the impact force of the finger 36 upon the shoulder 37 is reduced or minimized in the manner pointed out, thus substantially eliminating undesired noise and other defects during high sewing or operating speeds.

The section B of the operating path of the finger 36 of relatively small curvature is followed at point 5 by the section C of greater curvature in the opposite direction or away from the shoulder 37. While passing through the section C the finger 36 acts to instantly and quickly release, immediately after the escape of the needle thread from the gap between the tongue 28 and abutment wall of the notch 30, the shoulder 37 of the bobbin case 24, allowing thereby the needle thread loop to safely and readily pass about the bob-bin case 24.

From the foregoing, it can be seen that the finger 36, by the actions of its first driving eccentric 31, operating in synahronism with the looptaker 18, and of its second driving eccentric 49, operating in synchronism with the main drive shaft 3, perform an idle movement or oscillation during each revolution of the shaft 3 or stitch-forming cycle, respectively, as indicated in dotted line by the section D, that is, the finger 36 does not engage the shoulder 37 during the idle revolution or executes an operative movement along sections B-C solely during the loopseizing and casting revolutions of the looptaker, for the opening of the needle thread escape gap between the tongue 28 and abutment 30, in the manner described hereinbefore. This, in turn, results in a further reduction of impact noise, aside from the smooth operation of the opener during the operative (loop-seizing) looptaker revolutions, enabling thereby the machine to be safely operated at substantially high sewing or operating speeds.

The shape of the path of the opening finger 36, determined by the location of the two eccentrics 31 and 49 rotating at different operating speeds and resulting in the composite movement of the finger or bobbin case opener in two coordinate directions, that is, both radially and rotationally in respect to the opener member 35, may be varied, within certain limits, by a mutual adjustment of the eccentrics 31 and 49 upon their respective driving shafts, to suit any existing operating conditions or requirements. As an example, it is possible thereby to adapt the tangential section (4-5) of the operating path of the finger and/or its angle of attack upon the shoulder 37 for use with threads of varying diameter and other characteristics. In order to effect this adjustment, it is sulficient to provide for setting or adjusting the eccentric 49 upon is driving shaft, that is, shaft 9 (FIG. 2), shaft 52 (FIG. 4), shaft 56 (FIG. 6), and shaft 73 (FIG. 8).

In brief, the shape of the operating path of the finger 36, FIG. 5 is predicated in the first place on the different driving speeds of the eccentrics 31 and 49, resulting in the change of the extent of the path during alternate revolutions of the opener, as indicated by the full and dotted lines, respectively, in the drawing, and, in the second place, upon the mutual phase or adjustment of the eccentrics relative to their respective drive shafts, to control the angle of attack of the finger, or curvature of the path sections B and C, in the manner and for the purpose as described hereinbefore.

From the foregoing it follows that the positive operation of the bobbon case opener by virtue of its being in continuous force-locking engagement with the bobbin case, makes it possible to effect an accurate and reliable control of the needle thread escape gap during the loop seizing revolutions of the looptaker, during relatively high sewing or operating speeds and substantially without involving the defects and difficulties encountered with conventional bobbin case openers for rotary looptaker lockstitch sewing machines.

In the foregoing, the invention has been described in reference to a few exemplary and illustrative devices. It will be evident, however, that variations and modifications, as well as the substitution of equivalent parts and devices for those shown for illustration, may be made without departing from the broader scope and spirit of the invention. The specification and drawings are accordingly to be regarded in an illustrative rather than-a restrictive sense.

We claim:

1. In a lockstitch sewing machine having a reciprocatory needle, a main drive shaft with means to reciprocate said needle once during each revolution of said shaft, a rotary looptaker having a looptaker shaft wtih means to rotate the same by said main drive shaft at a speed being a whole number multiple of the speed of said main drive shaft, and a bobbin case frictionally mounted in said looptaker and having a shoulder and a rotationrestraining tongue, a stationary abutment, said rotationrestraining tongue engaging said stationary abutment, a bobbin case opener including means to intermittently open a needle thread escape gap between said tongue and abutment, comprising in combination:

(1) a first eccentric driven by said looptaker shaft,

(2) a ring-shaped opening member embracing said eccentric and having an eccentric arm terminating in a pivot, whereby to impart to said member a first radially oscillating component movement about said eccentric,

(3) an opening finger controlled by said member and having an end adapted for cooperation with said shoulder of said bobbin case, to rotate said case in a direction opposite to the direction of rotation of said looptaker, and

(4) a second eccentric driven by said main drive shaft and motion-transmitting means therebetween and said member, to impart thereto a second rotational oscillating component movement about said first eccentric.

2. A bobbin case opener as claimed-in claim 1, said first and second eccentrics being adjustable relative to one another such as to cause said finger to engage said shoulder during the loop-seizing revolutions only of said looptaker.

3. A bobbin case opener as claimed in claim 1, said first and second eccentric being adjustable relative to one another to result in a predetermined composite operating path of said finger by superimposition of said first and second component movements, whereby to cause said finger, during the loop-seizing revolutions of said looptaker, to initially relatively gradually engage said Shoulder, to result in a slow opening of said gap, and to become subsequently relatively rapidly disengaged from said shoulder accompanied by a quick opening of said gap.

4. A bobbin case opener as claimed in claim 1, including a ballbearing interposed between said first eccentric and said member.

5. A bobbin case opener as claimed in claim 1, whereing said motion-transmitting means consists of a linkage mechanism operably connecting an eccentric arm of said second eccentric with said pivot.

6. A bobbin case opener as claimed in claim 1, said opening finger being fast upon and extending from said member.

7. A bobbin case opener as claimed in claim 1, said motion-transmitting means comprising first and second connecting arms each having an end embracing, respec tively, said first and second eccentric and having their remaining ends connected by said pivot, said opening finger forming an extension of said second connecting arm.

8. A bobbin case opener as claimed in claim 1, including means to adjust said second eccentric relative to said main drive shaft.

9. A bobbin case opener as claimed in claim 1, said motion transmitting means comprising a slidably mounted push rod operably connected, respectively, through a pair of links to said member and an eccentric arm of said second eccentric.

10. A bobbin case opener as claimed in claim 1, wherein both said eccentrics are coaxial with said looptaker drive shaft and wherein said motion-transmitting means consists of a two-arm angular lever journalled upon a stationary shaft and connected by a link and ecentric arm, respectively, to said member and said second eccentric.

References Cited UNITED STATES PATENTS H. HAMPTON HUNTER, Primary Examiner 

